T. rex Body Temperature Measured at 36°C via Clumped Isotopes in Tooth Enamel

The study refined a decade-old clumped-isotope technique to use 90 percent less enamel, published September 16 in Science Advances. Tiny samples from two teeth belonging to the most complete T. rex at the Natural History Museum of Los Angeles County were analyzed for the temperature-dependent frequency of rare isotope bonds formed during enamel mineralization. This approach bypasses bone remodeling issues and yields a body-temperature estimate tied directly to the animal’s physiology at the time the teeth formed.

Results place T. rex at 36°C, warmer than living reptiles (28–30°C) yet cooler than most birds (40–43°C). The value aligns with prior indirect evidence of polar tolerance and active foraging, indicating an elevated metabolism that likely supported sustained activity without full avian endothermy. The intermediate temperature also implies efficient internal heat generation scaled to a multi-ton body without the overheating risk faced by smaller, fully tachymetabolic animals.

Context from related isotope work on other theropods suggests metabolic elevation may have been widespread among large carnivorous dinosaurs, potentially explaining their dominance across latitudinal gradients. The current measurement remains limited to two teeth from a single individual, however, so population-level or ontogenetic variation is unknown. Expanded sampling across growth stages and geographic populations would test whether 36°C represents a species norm or a local adaptation.

Next steps include applying the reduced-sample protocol to additional tyrannosaurid and non-tyrannosaurid taxa to map metabolic diversity before the end-Cretaceous extinction, with museum collaborations likely to accelerate data collection within three years.